Traditional low cost audio amplifying circuit used by consumer electronic products makes use of class A amplifier or push-pull amplifier. Current driving class A amplifier is very popular in low end voice synthesizing chips, melody chips and sound effect chips due to its simplicity and low cost. The major disadvantage of the class A amplifier and push-pull amplifier is the poor power efficiency. Another disadvantage of the single transistor class A amplifier is that the output signal usually suffers from the nonlinear distortion resulted from the nonlinear transfer curve of the driving transistor. The objective of the invention is to develop a low cost high efficiency analog signal amplifier particularly suitable for use to drive an audio signal to a speaker.